Field of the Invention
The present invention relates to an electroconductive member for electrophotography, a process cartridge and an electrophotographic apparatus.
Description of the Related Art
In an electrophotographic apparatus, that is, an image forming apparatus employing an electrophotographic method, electroconductive members are used for various purposes, for example, as a charging roller, a developing roller and a transfer roller. It is necessary to control the electrical resistance value of such an electroconductive member used in an electrophotographic apparatus to be 103 to 1010Ω, and for this purpose, an electron conducting agent represented by carbon black or an ion conducting agent such as a quaternary ammonium salt compound is incorporated into the electroconductive member.
An electron conducting agent such as carbon black is used as a conducting agent for various electroconductive members because the electrical resistance value is not affected by use environments such as a temperature and a humidity. It is known, however, that if an electroconductive member is provided with conductivity by using an electron conducting agent such as carbon black, there is a possibility that non-uniformity in the electrical resistance value of the conductive member may be caused due to non-uniform dispersion of the electron conducting agent. In particular, it is extremely difficult to prevent a portion or site having a lower electrical resistance value from occurring locally in the conductive member due to aggregation of the electron conducting agent.
On the other hand, in an electroconductive member into which an ion conducting agent is incorporated, the ion conducting agent is dispersed at the molecular size level, and hence, the non-uniformity in the electrical resistance value can be reduced as compared with the case where an electron conducting agent is used. The resultant electroconductive member has, however, a disadvantage that the electrical resistance value is largely varied depending on the temperature and the humidity of the use environment. It is known that there is a possibility that the electrical resistance value becomes higher due to drying of the electroconductive member particularly under a low-temperature and low-humidity environment of a temperature of 15° C. and a relative humidity of 10% (hereinafter sometimes referred to as “under the L/L environment”).
Thus, it is difficult to achieve both reduction of the non-uniformity in the electrical resistance value of the electroconductive member due to the non-uniform dispersion of the conducting agent and inhibition of the variation in the electrical resistance value of the electroconductive member due the use environment. In order to improve this issue, in Japanese Patent Application Laid-Open No. H09-101650, a raised electroconductive fiber entangled material is provided on the surface of a charging member for attaining uniformity in the electrical resistance value on the surface of the charging member. Alternatively, in Japanese Patent Application Laid-Open No. 2008-276026, roughening particles are dispersed in the surface layer of a charging member, so as to improve discharge non-uniformity caused by the increase in the electrical resistance value under the L/L environment.